Calculating and charting monthly data from a total duration

You would then fire an automation which would initiate when a project is created or modified and any relevant dates change.

Automation would update a single field and a single record on a single table with the record ID of the focus project.   The record idea of that single record in this automation control table will be 1 obviously as you will enter one and only one record.   

Then do a reverse relationship to the table so that one project has many admin focus records.  Even though there is only one admin focus record.  Look up key information from the focus project into that single record.  Then look up information from that single record down to the 1000 month field. table.  There will be a formula on those thousand records to calculate the first day of the month starting at the project start date and ending at the project and date. Any of the 1000 month records which are not needed will calculate to know dates.

Then the automation will Delete any project month records that already exist and then it will run to save table to table copy to re-create child project month records for the focus project..

So one project has many project month records and they will be maintained by the automation so that each project has the correct number of project month records as children they will have the correct dates on them and they can then self calculate their prorated share of the project cost divided by the number of project month record.